1. Technical Field
The invention is related to magnetic recording heads in a direct access storage device such as a disk drive, and in particular to gimbals and suspension assemblies employed therewith.
2. Background Art
The recording head in a direct access storage device (DASD) is constrained to allow rotational motion about the x and y axis, and translation along the z axis (see FIG. 1), but to disallow translation along the x and y axis, and rotation about the z axis. In practice, complete selective rejection of the undesired motions is not possible, but is approximated by mounting the head on a small metal structure commonly called a "suspension assembly". The suspension assembly is comprised of two parts with distinct functions: the "load beam" and the "gimbal" (see FIG. 2).
The load beam provides high compliance to translation of the head along the z axis only, and forms an otherwise rigid link connecting the head to a positioning means, such as an actuator mounting block. The gimbal has high compliance to rotary motion of the head about the x and y axis ("pitch" and "roll" compliance, respectively) and comparatively low compliance to all other head motions. Thus, the ideal gimbal would have zero rotational stiffness about the x and y axis, infinite rotational stiffness about the z axis, and infinite translational stiffnesses along all three axis. The width of the ideal gimbal would not exceed that of the head in a rotary actuated DASD. If this design specification is satisfied, the head can be brought as close as possible to the disk inner diameter without gimbal interference with the spindle hub.
Practical gimbal designs attempt to approximate the ideal gimbal while minimizing cost and mass. Mass is minimized so as to allow a rotary actuator to impart accelerations to the DASD sub-assembly known as the head/gimbal assembly (HGA), consisting of the recording head and suspension assembly.
Prior gimbal designs that increased roll or pitch compliance to improve performance suffered a corresponding loss in lateral stiffness, which reduced overall performance. Accordingly there is a need for a gimbal which provides greater pitch and roll compliance without sacrificing lateral stiffness.
Increasing vertical stiffness of the gimbal for greater dimple preload force reduces the tendency of the dimple to slip across the load beam. However, such an increase in stiffness in prior gimbal designs has prevented an increase in roll and pitch compliance. Accordingly, there is also a need for a gimbal which provides greater dimple preload force without a corresponding sacrifice in roll and pitch compliance.